Harry and Alex are brothers stuck spending a few weeks at Camp Spirit Moon. Though they wanted to go somewhere else, their parents waited too long and it was the only place left. After arriving, they find the camp empty and deserted. One counselor shows up and tells them that everyone left them there alone. Just as he starts freaking out, he bursts out laughing and tells them it was just a joke they play on all new campers.
Uncle Marv, the man who owns the camp, comes in and tells them that they can meet the other campers at the campfire that night. He makes some cryptic comments, and his eyes seem to glow when Alex asks if he can sing. Apparently Alex is some extremely talented singer. They go to their cabin, but it's all pretty boring. Worth noting is that Harry steps in a blue puddle that causes his feet to stick to the floor.
At the campfire, Alex meets a kid named Elvis and Harry meets a girl named Lucy. When Harry accidentally drops his hot dog in the fire, she reaches in and pulls it out. Even though he saw flames all over her and spreading up her arm, she's totally fine.
Then it comes time to sing the camp song. Alex goes overboard, and Elvis tries to keep up with him but he has a terrible voice. We have the spirit – and the spirit has us is some random line that keeps repeating in the song. Harry gets a little creeped out by the song and slips away from the group, only to hear Lucy calling his name and begging for his help.
Before she can tell him what she needs, Uncle Marv interrupts them and teases them about sneaking away in front of the whole group. He then sits them down and tells them some lame ass story. A bunch of kids and their counselor went into the woods, they went too far, and heard some odd noises. A big monster jumped out and ate them all. Elvis swears the story is completely true.
The second story involves a dense and heavy fog sweeping over a camp as a bunch of campers and counselors were sitting around a campfire. The fog was so heavy that they couldn't see anything. When the fog rolled away, everyone was dead. They just went back to their cabins and continued being undead.
Just then, a heavy fog really does come in and roll across them. Uncle Marv suggests that they sing the camp song again. Harry notices that the voices keep disappearing until only Alex's voice is left. When the fog leaves, they're all alone. Harry realizes that it's just another prank and that they probably used a fog machine. When they get back to the cabins, everyone makes fun of them and teases them. Though he laughs it off, Harry does notice that those weird blue puddles are back again.
Harry also notices that two of his cabin mates seem to have eyes that glow in the dark and wakes to find one of them floating in the air. Though he convinces himself that it was just a dream, weird things keep happening. One kid gets a sharp tent stake right through his foot and is fine, another is fine after someone stabs him in the neck with a fork. Alex saves a little girl he finds sitting on the bottom of the lake for 10+ minutes and she just laughs at him. Plus, they both see a girl's head fall off during a soccer game.
Lucky keeps following Harry around and finally tells him the truth. The stories actually happened and everyone there is a ghost. Instead of calling the loonie bin, Harry believes her. Lucy then tells him that he can save them if he lets her possess his body for awhile. When she tries, he runs for the hills.
Okay, so he really just runs back to the cabin, grabs Alex, and drags him into the woods. Alex reveals that Elvis tried to do the exact same thing to him, so he knows that they really are ghosts. They make plans to find the highway and run away, but then they hear a noise coming from the woods and the monster from the one story attacks. No worries though, Alex has a plan.
They basically close their eyes and say that they don't believe that the monster exists, which causes it to disappear. Uncle Marv and the other campers then show up. It turns out that they need a living body to escape the camp. Lucy attacks Harry, while Elvis grabs Alex. They all start fighting, and somehow during the fight, they all disappear.
Harry and Alex run off to find the highway and get in touch with their parents. When Alex starts humming off-tune, Harry realizes that he's actually Elvis. In the end, Elvis promises that he'll never sing again if Harry doesn't tell on him. Sure kid, I'll let you possess my brother.